Target for color characterization of color printer

Abstract

With respect to color characterization of color printers, the present disclosure relates to the identification of colorant combinations for color patches in a color characterization target, which contains different color patches, and which is measured calorimetrically or spectrally to color-characterize the printer. A black ramp is printed and measured. Substantially uniform steps on the ramp are selected by applying principal component analysis to the measured values or color values derived from the measured values, and by using a first principal component thereof to select the substantially uniform steps. For each of the substantially uniform steps identified, the above procedure is repeated on all chromatic ramps with black ink at a corresponding black level. Color values of the color patches are populated by using multiple combinations of the substantially uniform steps of the black channel and of the chromatic channels at the corresponding black levels that meet an ink limit.

Description

BACKGROUND[0001]1. Field[0002]The present disclosure relates to a color characterization of color printers. More precisely, the present disclosure relates to the identification and selection of colorant combinations for color patches in a color characterization target, which is printed by a printer and which contains multiple different color patches, and which is measured colorimetrically or spectrally so as to color-characterize the printer.[0003]2. Description of the Related Art[0004]Known techniques for color-characterization of a color printer typically involve the printout by the printer of a color characterization target which contains multiple differently colored patches. The color patches are measured calorimetrically or spectrally. Based on a mapping between the colorant values that created each color patch, and the spectral or colorimetric measurement of each such color patch, the color performance of the printer can be derived and characterized.[0005]Recently, two technol...

AI Technical Summary

Benefits of technology

The present invention relates to a method for selecting colorant values for a color characterization target, which involves determining a practical number of color patches that tend to fill the color space of the printer. This results in good color characterization of the printer regardless of the color measurement technique used. The method involves a multi-step process of determining colorant values for the color patches, including printing and measuring color values, applying principal component analysis to the measured color values, and selecting substantially uniform steps that are substantially invariant to small variations in the first principal component. The resulting printable target contains a reduced number of color patches that meet the ink limits of the printer, and good spectral or colorimetric characterization can be achieved. The method also allows for easier comparison of multiple runs of the color target.

Problems solved by technology

Recently, two technological and marketplace developments have converged that tend to increase the burden involved in characterization of a color printer.

The complexity of the mapping between colorant values and color measurements also increases with an increased number of color patches.

As a result, with four or more colorant channels, the burden of printing multiple patches, measuring them, and mapping them, also increases geometrically.

In addition, the complexity of the mapping between the colorant values and the spectral measurements is also increased significantly.

Such a large number of color patches would be impractical to print and to measure, especially for a spectral characterization.

Moreover, even if all 15,625 patches were printed and measured, the resulting data set might be too computationally intensive to yield a good color characterization.

While such differences might not be significant to ensuing colorimetric or perceptual uniformity, such differences can often cause difficulties to color scientists and printer R&D engineers, who are trying to compare one run against another.

Furthermore, this tends to exclude very dark color patches, whose measurements tend to be noisy and thus detrimentally affect mapping anyway.

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